Conductive metal oxides have been investigated in the context of electronic, plasmonics, and optical technologies. Some interest in plasmonic technologies may be based on emergent optoelectronic applications, such as plasmon lasers, transistors, sensors, and information storage. While plasmonic materials, such as gold and ITO, have been found for use in UV-VIS and near infrared wavelength ranges, the mid-infrared wavelength range may be more challenging to address, for example, due to lower free carrier mobility values (i.e., higher plasmonic loss) that may be common in conductors with carrier concentrations that support plasmonic resonance in the infrared wavelength range.
Electron mobilities surpassing 500 cm2/(V·s) at carrier densities greater than 5×1019 cm−3 have been demonstrated in dysprosium (Dy)-doped cadmium oxide (CdO) (notated herein as CdO:Dy). These transport properties can satisfy the criteria for mid-infrared spectrum plasmonics, and can overcome the optical losses seen in some conventional conductors, such as noble metals.
Molecular beam epitaxy (MBE) may allow for precision doping to achieve such properties. However, the sophistication of MBE instrumentation may present some barriers with respect to material implementation. As such, alternative process methods to manufacture doped cadmium oxide thin films, such as metal-organic vapor phase-epitaxy, pulsed laser deposition, colloidal nanocrystals, and radio frequency sputtering, have been explored.